I am reading HtDP (https://htdp.org/) at the moment. I am quite liking its style. What to do after that? I want to build a solid base of CS fundamentals. Like programming high level as well as low level, different paradigms, algorithms, basics of TCS and other applications.<p>What are some good foundational books in each area that teach timeless concepts and not just some fancy tool that is currently popular?<p>If there are available online courses (not like those shallow ones in MOOC platforms) with public materials let me know about them too.